A public servant and a former National Australia Bank employee have pleaded guilty to a multimillion-dollar insider trading scheme.

A banker told his partner in an insider trading scheme to keep his spending under wraps, despite buying a property from a reality TV show and reaping millions from a secret second account.

Former National Australia Bank (NAB) employee Lukas James Kamay netted more than $7 million in profits after receiving market-sensitive data from Australian Bureau of Statistics (ABS) worker Christopher Russell Hill before its official release.

Kamay, 26, and Hill, 25, pleaded guilty to insider trading in the Melbourne Magistrates Court on Tuesday.

Documents tendered to the court say the pair, who studied together at Monash University, devised the scheme after being reunited at a mutual friend’s birthday party in 2013.

Kamay and Hill had aimed to make $200,000 from foreign exchange derivative trades in a 12-month period and then quit, splitting the profits equally after tax.

They were on their way to reaching their goal and, without his partner’s knowledge, Kamay also ran a second trading account, the documents show, which reaped most of the more than $7 million in profits.

In April this year, Kamay agreed to buy a property featured on TV show The Block for $2.375 million.

Two weeks later, Kamay told Hill to be careful with how he spent his money and not to make any big purchases.

“I’ve been very conservative,” Kamay said in a conversation covertly recorded by the Australian Federal Police.

“I haven’t told anyone at work, no one, not even my girlfriend knows about this. Have you kept it like that way as well?”

During the conversation, Hill told Kamay that no one at the ABS would suspect him because it was part of his job to look at the data.

The two communicated through prepaid mobile phones in false names, after Hill obtained personal details from his tenant and Kamay did the same to a man applying for a job at NAB.

The documents show the windfalls reaped by Kamay’s trades grew larger as time went on, and he deliberately traded to make losses in an effort to avoid scrutiny.

Kamay, of Clifton Hill, pleaded guilty to six insider trading charges but pleaded not guilty to a charge of dealing with the proceeds of crime.

Hill, of Belconnen in the ACT, pleaded guilty to six offences, including insider trading and abuse of a Commonwealth office.

Both men have been granted bail to face a directions hearing in the Victorian Supreme Court on October 1.